Many types of excavating equipment utilize replaceable ground-engaging teeth. These teeth erode through use and are frequently replaced. Depending on the conditions, a given support structure or adaptor would be re-equipped with from 5 to 30 teeth to maintain a sharp penetrating edge during excavation. The ease of replacement of the teeth is important because it minimizes the amount of wasted throw-away material and also minimizes the downtime of the tool.
The prior art assemblies used to attach a tooth to the adaptor consist mainly of two designs, the wedge design and the pin design. In the wedge design, the tooth is joined to the adaptor by wedges which are hammered into corresponding slots in the tooth and the adaptor. This design has the disadvantage that the wedges would often become dislodged during use of the excavating equipment. To prevent this problem, the wedge was tack-welded in place. However, removal of the wedges became difficult and time consuming. It also required the drag-line bucket, for example, to be turned on its front end to gain access to the wedges. Further, during removal, the wedges had a tendency to shatter or break causing pieces to jam in the slots and posed a serious safety hazard to workers. Wedge designs are shown, for example, in U.S. Pat. No. 3,256,622.
Pin assemblies are shown in U.S. Pat. No. 2,121,993. This patent discloses a threaded pin and insert assembly for securing a tooth onto the adaptor. The threaded insert is placed into the adaptor pin opening. The tooth is placed over the adaptor. A lock washer is concentrically placed over the pin opening on the tooth. The pin is then screwed into the insert. This assembly had the disadvantage of being cumbersome and complex in design making it difficult to use and increasing the time needed to replace the tooth. As well, the pin has a tendency to loosen from the insert while the tooth is in use. Another pin assembly is shown in U.S. Pat. No. 3,410,010 which discloses a dipper tooth having a detent and key assembly inserted into a passage in the tooth and adaptor. This assembly suffers from the drawback that the key would often fall out of the passage during use of the tooth allowing the tooth to fall off the adaptor.
These wedge and pin assemblies were used not only for attaching ground-engaging teeth to adaptors on excavating equipment but also for attaching other types of wear members to support structures such as for example, attaching a protective lip shroud to a bucket lip.
There is therefore a need for an assembly to attach a removable wear member to a support structure in such a way that the assembly is easy to use, reliable, and economical to manufacture. The assembly needs to be easily installed and removed without the use of force or impact on the locking device. It needs to be easily installed and simple to remove so that wear member changes can be accomplished with minimum effort and maximum safety. It needs to remain functional throughout its service life so that even after a long period of use, it can still easily release a worn-out wear member that is due for replacement.